This invention relates generally to excitation systems for synchronous generators. In particular, the invention relates to modeling of excitation systems.
Excitation systems are used to produce a dominant magnetic flux in synchronous generators. Synchronous generators typically have a controller for their excitation systems. It is common practice in the industry to produce a tailored IEEE (Institute of Electrical and Electronics Engineers, Inc.) model of the excitation system of a particular industrial generator.
Various generic excitation models have been endorsed by IEEE committees as standard models for use in modeling specific excitation systems. Each of these standard models is a simplified control block diagram with parameters that can be tailored to mathematically match the response of a particular excitation system to certain data inputs. Each model has certain parameters: variables and constants. The constants can be set to tailor the IEEE standard model to simulate the operation of a specific excitation system. The tailored IEEE excitation model is used to simulate the operation of the excitation system for various purposes. One purpose of the model is for use in power system study work, including optimization of the excitation system and its associated generator to improve overall system stability and reliability.
To model a specific excitation system, the appropriate IEEE standard model is selected and is initially tailored based on pre-calculated data obtained for the excitation system. To tailor the IEEE standard model, engineers use pre-calculated data to set parameter values in the selected IEEE standard model. Parameters are first estimated based on known information regarding the exciter. These estimates are determined before the exciter is placed in operation with the generator at a customer site. The selected IEEE standard model is usually further tailored (typically at a remote site away from a customer generator site such as at the site of the manufacturer of the excitation system) using test data obtained on site directly from the exciter and generator.
After the IEEE standard model has been tailored using data obtained from on site testing, additional on site generator testing may be performed to verify the accuracy of the tailored IEEE excitation model. Expert personnel are typically needed at a customer site to perform verification tests of the tailored model. It was not uncommon for extra test and measurement equipment to be brought to site for testing. If a significant discrepancy is detected between the tailored IEEE excitation model and the data obtained from the actual excitation system during on site testing, the tailored IEEE excitation model was updated and reissued. A multi-step analysis performed by experts may have been required to prepare a final IEEE model. The report is generally given to the customer-owner of the generator to document the operational state of the excitation system.
If expert personnel are not on site to verify the tailored IEEE excitation model, less experienced personnel typically perform specific tests and collect data regarding the on site operation of the excitation system. Experts at a remote location may later analyze the collected data to verify the tailored IEEE model. If the collected data was found in error, the testing may have had to been repeated which required an additional visit to the customer site.
In the past, the data recording, analysis, and reporting systems were not fully integrated with the excitation system and its configuration tools. Generation of an accurate and verified IEEE excitation model has often required multiple efforts of selecting a standard model, collecting data from the exciter, tailoring the standard model with the data and verifying the tailored model. This multi-step process has been time consuming, expensive and error prone. There is a long felt need for a more efficient system and method to select an appropriate IEEE standard model, collect test data from the excitation system, tailor the selected standard model, and verify the tailored model.
There is a need in the art to reduce the time and cost of producing an accurate IEEE model of an excitation system. This need includes a better means to identify the characteristics of the excitation system and to predict system performance. There is also a desire to reduce the time needed to test regulator and limiter functions, and it is preferable to conduct on site tests without experts at the site. There is a further need to produce a customer oriented report promptly following site testing.
Further, a validated and tailored IEEE model of an excitation system can be used to optimize the settings of an operational excitation system and generator. Optimization typically involves determining the output responses to the model of a large number of possible input values to the excitation system. The optimization process typically involves many cycles of applying various values of inputs to the model and evaluating the responses of the model. There is a long felt need for a method to optimize the excitation system with fewer cycles of various possible inputs.